When i minimise any app in my iPhone Does that app runs in background? or Pauses? or stops the app ?

I have a doubt that i have iPhone 3G and iPhone 4 both and if i run my app and test in those devices like if i press the home button of my iPhone and open some other app and again if i open my app, in iPhone 4 my app opens the screen where i minimized it , in iPhone 3 my app starts from splash screen i mean the app restarts from beginning. I don't know why this is happenin开发者_高级运维g is this my code problem or this is the iPhone's multitasking problem? When i minimize any app in my iPhone Does that app runs in background? or Pauses? or stops the app? what actually happens when i minimize my app in both generation phones Any help is appreciated in advance thank you.

The app goes to the background and stays there as long as it can. If memory gets short, the app terminates.

How the device handles background application is more a function of the iOS than the device. Even 2nd generation phones running iOS 4.0 have multitasking.

iPhone 3G doesn't support multitasking, only 3Gs, 4 and iPads. As for background tasks, you have to implement background functionality, like playing music or downloading something or sending local notifications, by yourself.

Look at UIApplicationDelegate Protocol Reference. In discussion part of method called applicationDidEnterBackground: you can find answer on your question.